The invention relates to a control system having at least one electronic control unit for controlling an internal combustion engine in a hybrid vehicle.
Hybrid vehicles have already been known for many years, including as mass-production vehicles, which contain at least one internal combustion engine and at least one electric motor as drive motors. Such hybrid vehicles have control systems with at least one electronic control unit, which in particular through correspondingly programmed function modules carry out various operating procedures for the selection of an operating mode that is adapted to the respectively current driving situation. Operating modes which are able to be selected are, in particular, purely electric driving (only the electric motor is driving: “E-mode”, “E-driving”), driving purely by the internal combustion engine (only the internal combustion engine is driving), and/or hybrid-driven driving (both the electric motor and also the internal combustion engine are driving).
Primarily, known operating methods take into consideration the charge state of the battery or of another electric reservoir (e.g. super-cap) for the selection of the operating mode. In part here also parameters such as the current vehicle speed, the current driving performance or particular currently set customer functions are taken into consideration.
It is an object of the invention to further improve a control system with an operating method of the type described above.
This problem is solved according to the invention by a control system having at least one electronic control unit for controlling an internal combustion engine in a hybrid vehicle, wherein the control unit is configured such that it evaluates input signals for detecting data for identifying a current situation and for detecting at least one situation forecast in the near future with respect to an expected speed curve. The control system controls the restart and shutoff of the internal combustion engine at least depending on the expected speed curve.
The invention comprises generally a method for controlling the restart and the shutoff of an internal combustion engine in a hybrid vehicle, wherein by an evaluation of the current situation and of situations lying ahead, preferably in a defined forecast range, with regard to an expected speed curve and preferably also to a load curve as a function of a driver interaction and/or of the charge state of the high-voltage reservoir, the restart and shutoff performance is optimized in a defined manner, which will be discussed more precisely further below.
According to the invention, basically data for identifying a current situation and for identifying at least one situation prevailing in the near future (e.g. defined forecast horizon <5 km) are detected and evaluated with regard to the expected speed curve. Such data for the forecast of the speed curve comprise, in particular:
(i) map data concerning environment and/or traffic routing information of navigation systems (e.g. ADAS with RTTI) and (driver-specifically) learning systems for the prediction of the most likely route lying ahead, for the prediction of speeds in curves lying ahead, for the detection of speed limits lying ahead and current speed limits, for the prediction of the gradient of the route lying ahead, for the prediction of the average speed as a function of the traffic density on the route lying ahead, etc.,(ii) sign recognition systems (e.g. KAFAS), in particular for the recognition of traffic signs with an influence on the speed which is to be expected,(iii) camera systems for detection of the current state of the lying-ahead and relevant signal light system (identifying of the traffic light status) and (learning) systems in the vehicle or via backend for the chronological prediction of the relevant signal light systems (forecast of the traffic light status),(iv) vehicle sensor technology (e.g. radar and KAFAS) for the detection of other road users driving ahead (in particular speed and acceleration of the preceding vehicle), and/or(v) all further systems which can contribute to a prediction of the expected speed curve.
Furthermore, preferably at least one driver interaction is determined, in particular through the detection of the accelerator pedal position of the respectively current load demand.
According to the invention, the restart and shutoff of the internal combustion engine is controlled primarily depending on the expected speed curve and the expected load curve in the predetermined forecast horizon and preferably also on current driver interaction. Furthermore, the restart and shutoff performance is optimized as a function of the operating state of the vehicle, such as in particular the charge state of the high-voltage reservoir.
The expected speed curve is preferably compared with the usual charge-state-dependent fixed maximum E-driving speed limits for purely electric driving (E-mode) in a charged state (CD=“charge depleting”, upper E-driving speed limit) and in the discharged state (CS=“charge sustaining”, lower E-driving speed limit). When the currently valid E-driving speed limit is fallen below by the actual speed, according to the prior art the internal combustion engine is shut off immediately. When the currently valid E-driving speed limit is exceeded by the actual speed, according to the prior art the internal combustion engine is restarted immediately. Furthermore, according to the prior art, a restart or respectively shutoff also takes place outside these speed limits, in so far as load limits dependent on speed and on charge state of the battery are exceeded or respectively fallen below. Through the invention, in particular the expected speed and load curve and not only the current speed and the current load are considered with regard to these hitherto rigidly set limits. The new situation(s) lying in the near future can lead, according to the invention, to the (continuous) shifting upward and downward and/or to the ignoring of these restart limits which were hitherto predetermined in a situation-independent manner.
The control by means of the control system according to the invention, or respectively the method according to the invention, for controlling the restart or shutoff of an internal combustion engine is carried out in a defined manner, namely preferably such that                phases with only a briefly shut off or only briefly restarted internal combustion engine are prevented,        the E-mode with a comparatively low load is maintained for as long as possible, or with a comparatively high or increasing load is prevented,        a restart of the internal combustion engine is carried out preferably during acceleration processes and not during steady speed,        long decelerations which are to be expected are preferably travelled with the internal combustion engine shut off, and/or        the number of restart and shutoff procedures are reduced in client operation.        
In an advantageous embodiment of the invention, proceeding from a purely electric driving state with acceleration to be expected to a value above the upper E-driving speed limit, a restart of the internal combustion engine is carried out already on increase of the load demand or respectively at the start of the acceleration and not only on exceeding of the largely static E-driving speed limit or respectively load limit.
In a further advantageous embodiment of the invention, the shutoff of the internal combustion engine is prevented if through a deceleration an only brief falling below of the E-driving speed limit is expected. Therefore, a renewed internal combustion engine restart shortly after its shutoff is prevented.
In a further advantageous embodiment of the invention, the shutoff of the internal combustion engine is carried out with deceleration which is to be expected until below the E-driving speed limit prematurely already with the load relief still before falling below the E-driving speed limit. A prerequisite for this is that the deceleration lasts long enough or the further expected speed curve remains below the E-driving speed limit.
Furthermore, likewise with decelerations and coasting operations, the target speed of which lies above the E-driving speed limit, the internal combustion engine is shut off (prematurely) with the load relief, in so far as a long-lasting load-free travel or deceleration is to be expected (e.g. coasting on a downhill gradient). Preferably this is the case when the (premature) shutoff is classified to be of value to the customer and efficient.
Preferably, the restart of the internal combustion engine is basically prevented without load demand irrespective of the E-driving limits, as long as no acceleration is to be expected or is carried out. This means that a restart of the internal combustion engine is as far as possible “masked” by an acceleration process. Restart processes of the internal combustion engine during a steady speed are prevented.
According to the prior art, a restart of the internal combustion engine then takes place in so far as the charge state of the high-voltage reservoir has fallen too far. In a further advantageous embodiment of the invention, the restart limits dependent on the charge state of the high-voltage reservoir are adapted so that a restart of the internal combustion engine does not occur during a steady speed. Instead, the restart of the internal combustion engine takes place prematurely or belatedly by means of a masking during an acceleration. This means that the change of a charge depleting strategy (discharging of the high-voltage reservoir at sufficient charge state) to a charge sustaining strategy (holding the low charge state of the high-voltage reservoir) is shifted in a targeted manner, in order to obtain an operating strategy which has greater customer value and is more efficient.
Preferably, for acoustic and dynamics reasons, a restart of the internal combustion engine is basically carried out already at the start of an acceleration process and not only after exceeding the currently valid E-driving speed limit, i.e. possibly at high load of the internal combustion engine, when through the expected speed curve an exceeding of one of these two limits or a battery discharge is foreseeable.
In a further advantageous embodiment of the invention, a restart of the internal combustion engine due to load is prevented in so far as the expected speed curve lies continuously below the currently valid E-driving speed limit (e.g. owing to a continuous speed limit distinctly below the currently valid E-driving speed limit or a red traffic light lying ahead). This situation-dependent restart robustness therefore prevents a brief restarting of the internal combustion engine with short load requirements on the part of the driver, and therefore increases the E-driving experience from the customer's point of view.
In a further advantageous embodiment of the invention, the brief shutoff of the internal combustion engine with short vehicle stops (e.g. in front of stop signs, prediction of a short remaining red phase of the traffic light, etc.) is prevented, in so far as the low charge state of the high-voltage reservoir does not permit electric driving.
A further advantageous embodiment of the invention provides, with reliable detection of a beginning overtaking procedure (e.g. by means of blinker signal, identification of a tractor, slow preceding vehicle relative to the speed limit with, at the same time, low traffic density, etc.), a premature restart of the internal combustion engine. The aim is to increase the response and the dynamics for the overtaking procedure.
In a further advantageous embodiment of the invention, the control unit is configured such that a restart of the internal combustion engine is shifted to a later upcoming acceleration process, when through the expected change of the operating strategy modes from charge depleting (discharging of the high-voltage reservoir) to charge sustaining (holding charge state or respectively charging the high-voltage reservoir) in any case a restart of the internal combustion engine is necessary, which otherwise falls chronologically into a steady speed.
Through the invention, the following advantages are achieved:
1) Increase of the driving experience in the E-mode by
                extending of the driving phase in the E-mode (by means of reduction of restart due to load in expected low load situation)        optimization with regard to energy        restart robustness2) Improvement of acoustics and customer reproducibility of the operating strategy by        prevention of brief shutoff or respectively restart of the internal combustion engine        reduction of shutoff oscillations        restart robustness (in the lower speed band)        reduction of restart and shutoff processes in customer operation        prevention of restart processes at steady speeds (inter alia by means of masking in accelerations)        advancing of restarts before high load situations (prevention of high coupling rotation speed)3) Consumption reduction or respectively range increase by        prevention of unnecessary E-mode driving with expected high load        reduction of the restart losses by means of prevention of unnecessary shutoff processes        increased use of recuperation energy by premature shutoff of the internal combustion engine4) Sportiness or respectively response improvement by        prevention of only brief shutoff processes before high load situations        premature restart of the internal combustion engine before high load requirement        
Other objects, advantages and novel features of the present invention will become apparent from the following detailed description of one or more preferred embodiments when considered in conjunction with the accompanying drawings.